Follow-up data will include newly charted clinical, functional, and radiographic imaging data, including dynamic x-rays and CT scans to be obtained prospectively at a minimum of one (1) year post-operatively. During the routine post-surgical visits, patient pain outcomes are measured using the Visual Analog Scale (VAS) for back and leg pain, function is measured by the Oswestry Disability Index (ODI) and Short Form-12 Version 2 (SF-12 Version 2 Health Survey). A physician investigator will also perform routine clinical evaluations.